Magneto



Dec. 29, 1931. A, WATSON 1,838,339

MAGNETO Filed Sept. 29, 1950 2 Sheets-Sheet 1 E. A. WATSO N Dec. 29, 1931.

MAGNETO Filed Sept. 29, 1930 2 Sheets-Sheet 2 b Fig.4

Patented Dec. 29, 1931 UNITED STATES PATAENT'OFFICE ERNEST ANSLEY WATSON, OF WEST ORCHARD, COVENTRY, ENGLAND, ASSIGNOR TO THE M M-L MAGNETO SYNDICATE LIMITED, 01 COVENTRY, ENGLAND i MAGNETO Application filed se tem er'ze, 1930, Serial No This invention has for its object to provide an improved magneto adapted particularly for use with internal combustion engines. 1

The invention comprises a magnetic system consisting of a pair of parts arranged in parallel with each other, one part consisting of a permanent magnet, pole pieces, and a movable armature or keeper, whilst the other consists of a member which is separated from the first part by a suitable air gap or gaps, windings being arranged on both parts as hereinafter described, andjthe whole being adapted to operate as hereinafter described.

In the two accompanyingsheets of explanatory drawings Figure l is a sectional front elevation and Figure 2 a sectional end elevation of an ignition magneto constructed in accordance with this invention.

Figures 3 and 4 are respectively sectional front elevation and sectional plan of a magneto similar to that shown in Figures 1 and 2, but having a modified form of contact breaker.

Figure 5 is a diagram illustrating the windings used in the magneto.

Referring to Figures 1 and 2, one part of,

the magnetic system or circuit is in the form of a loop consisting of a permanent magnet a, a pair of pole pieces b respectively arranged at the ends of the magnet, and a movable armature or keeper 0 co-operating with the pole pieces. The armature is arranged to be reciprocated or oscillated with respect to the pole pieces from the position shown by full lines to such a position as is indicated by dotted lines. The armature is, as shown, constructed from laminations, and is attached to a cylindrical hollow guide stem p which can slide in the metal block Z situated between the pole pieces Z). The other part of the magnetic system comprises a core d in the form of bar or other suitable member which lies between the pole pieces b above mentioned and is arranged in parallel with the magnet so that it provides an alternative path for the magnetic flux. One or each end of this memher is separated from the first described part of the magnetic system by an air gap e of suitable size.

#485,214, and in Great Britain October 30, 1929.

The preferred arrangement of windings comprises a primary winding f on. each of the pole pieces I) with which the armature or keeper co-operates, and a primary winding 9 and secondary winding h on the core II. The a two windings f are in series orin parallel with each other and virtually form one winding. If desired, a single winding only arranged on one of the poles may be used. The polewindings is or are connected in parallel 50 with the other primary winding g, as is made clear by the diagram at Figure 5. A contact breaker connected to the junctions of the two primary windings serves to short circuit them, or put them into electrical connection.

The contact breaker shown in Figures 1 and 2 comprises a fixed contact 2' carried by an insulating piece on pillars 7a secured to a fixed non-magnetic metal block l located between the pole pieces I), and a movable contactpiece m on alplunger n which is carried in the stem ;0 of the armature c and is controlled by a spring 0.

In one position of the armature 0 the whole orthe greater part of the flux is confined to the first described part of the magnetic system, and little or no flux passes through the cord 0!. On moving the armature so as to increase the reluctance of the system (the contact breaker being meanwhile closed) a current is generated in the two-part primary winding on the pole pieces. Towards the end of the movement of the part 0 the contact breaker is opened, (by the engagement of a shoulder s on the plunger n with a shoulder q in the guide stem which carries the plunger) and the current so generated is caused to pass into the second primary winding 9 with which is associated the secondary winding 71., the latter serving to produce the necessary voltage for causing a spark in the engine. It will be seen that with the successive movements of the armature the flux is caused to flow alternately through the pole pieces and armature, and through the part of the system carryingthe secondary winding. By means of the contact breaker shown in Figures 1 and 2, the contacts 71, m remain in contact during a suitable time during the separation of the armature from the pole pieces, and 100 only separate after a suitable amount of movement has been given to the armature.

A condenser r is arranged in conjunction with the contact breaker in the usual way, and any convenient means may be employed for actuating the armature or keeper and the contact breaker.

Whilst I prefer to provide a primary winding in association with the secondary winding, this is not essential, as a secondary winding only may be provided on the second part of the system.

By this invention I am able to provide a very simple and compact magneto which for some purposes is more convenient than the machines commonly employed. Further I am able to secure the additional advantage that no demagnetizing action is exerted on the magnet in the normal working of the machine.

In the modification shown in Figures 8 and 4., a magnetically operated contact breaker is arranged at one side of the pole pieces Z). In conjunction with each of the inner vertical faces of the pole pieces is ar ranged a projecting subordinate pole piece t on one of which is pivoted a subordinate armature a by means of a spring blade 1). The part it carries a contact piece m which (BO-OPBI'RtOS with a fixed contact piece 2'. hen the main armature 0 makes contact with the pole pieces Z) practically no flux passes through the parts a, u, and the contacts i, m are pressed together by a spring 0. lVhen. however, the main armature 0 is moved away from the pole pieces 6, the reluctance of the magnetic path through 0 is increased, and flux is diverted to the parts a, causing the latter to be attracted to one of the subordinate pole pieces L and separating the contact pieces as shown in Figure 4. hen the main armature is returned, flux is withdrawn from the parts 2/, a, and the contact pieces again pressed together by the spring 0.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. A magneto comprising, the combination of a permanent magnet, a pair of pole pieces associated with the ends of the mag not, an armature movable relatively to the pole pieces, the pole pieces and armature providing a main flux path between the ends of the magnet, core providing an alternative flux path between the magnet ends and having associated with it an air gap of constant size, primary and secondary windings on the core, a generating winding situated in the main flux path in a position between the core and the armature, and means whereby the generating winding can be alternately short circuited and put into electrical conncction with the primary winding on the core, substantially as described.

2. A magneto comprising, the combination of a permanent magnet, a pair of pole pieces associated with the ends of the magnet, a reciprocator r armature movable relatively to the pole pieces, a core situated between the pole pieces adjacent to the magnet ends and having associated with it an air gap of constant size, a generating winding on each of: the portions of the pole pieces lying between the core and the armature, primary and secondary windings on the core, and a. contact breaker whereby the generating windings are alternately short circuited and put into electrical connection with the primary windiiw, substantially as described.

In testimony whereof I have signed my name to this specification.

ERNEST ANSLEY WA SON. 

